I have a question I think you guys might be able to help me with. If you have a loop of wire and move a piece ferrous metal in and out of it, the inductance changes. This I know. What I don't know is if the inductance also changes depending on where in the loop the metal is placed. Does the inductance change depending on how close or far the metal is to the edge? Or does it stay the same no matter where in the loop the metal is placed.

Yes, the reason I am trying to convert a sine wave into a square wave is so I can feed it into a PIC. In stead of using the ADC and a software algorithm to find the frequency, I thought it would be easier and less CPU demanding to use a square wave input where a pin change interrupt and a timer could be used to find the waves period/frequency. Do you think this is do-able

I was also thinking about AC coupling the signal. So I would feed the sine wave into the +input and hook the -input to ground? If I AC coupled the signal, does my picture look right as to how I am picturing it would work?

I have searched for "zero crossing detector" and all the circuits I see are for AC sine waves that are referenced around a positive supply, a negative supply, and a ground. In my situation, I only have 5v and GND, I do not have -5v.
The sine wave I am trying to convert into a square wave is biased at about 2.5v between the 0v and 5v rails . I am still searching, but I have not found a peak detector that works using a single supply. I would think a single supply peak detector exists because I thought they used in RF demodulators or discriminators.

I was wondering if I could borrow your guys' EE expertise. I have a project where I need to turn a sine wave into a square wave like in the picture. The project I have is to determine the roll position of a spinning projectile using thermopiles. My question I was hoping you electrical engineering guys could help me with is my need to get the sine wave's DC level. I was wondering what kind of circuit can do this?

I had not realized a patch antennas size is determined by its dielectric. Now that I think about it, I guess it does make sense. Darn, I thought making the antenna bigger would increase its gain. I should have known something that simple would be too good to be true.

I was wondering what the relationship is between a patch antenna's gain and its physical size is. If I wanted to say double a patch antennas gain (add an additional 3 dB), by how much do you increase its physical size. In other words, to add an additional X dB gain to the antenna, you take the current dimensions of the antenna and multiply them by a factor of Y. My question is how do you find Y given how much additional gain you want.
This where the confusion comes in. I know it isn't as simple as doubling the dimensions to double the gain because this is what you do to chance the antennas operating frequency. For example, if you multiply the dimensions of the antenna by two, you do not increase its gain, you decrease its operating frequency by half (ex. 2.4 GHz to 1.2 GHz for an antenna twice as big). So my question is what is the underlying theory behind a patch antennas size and its gain?

Does anyone know what is going on with Radiohound. I sent them a money order a few weeks ago for an order and it was returned to me today. Secondly, their site has been down since last week. Thirdly, I don't get any replies to emails from them. Does anyone have any insight?

I was looking at some low cost RF transmitters at Radiotronixs but they have relatively low output power. Would it be possible to simply add a RF amp module, something like this, or are using PA modules more involved than just soldering them in? I am interested in increasing the power to around 1 Watt.

I am trying to weigh the benefits of using Manchester coding and packet repetition and was wondering what your thoughts are considering how much interference is normally encountered out on the flying field. I am trying to decide on the most robust communication given the data rate tradeoff.
Send one packet: say 30 frames/sec
Send each packet twice (incase first packet has error): 15 frames/sec
Send one packet but use Manchester coding: 15 frames/sec
Send each packet twice using Manchester coding: 7.5 frames/sec
I am not sure what kind of interference to expect (random/burst/prolonged?) and was wondering what your thoughts are on the topic.